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XXV. On the Triple Prussiate of Potash. By R. Phillips,' 



F.R.S. L. 4- E. Sfc. 

 "CpEW substances have more occupied the attention of che- 

 -*■ mists, than the salt called triple prussiate of potash : but 

 notwithstanding the repeated examinations to which it has 

 been subjected, it will appear on referring even to the latest 

 chemical works, that great difference of opinion still exists, not 

 only as to the mode in which the elements of the salt are com- 

 bined, but even as to their number, nature, and proportions. 



It is not my intention to give a history of the various ideas 

 which have been entertained respecting this substance. I shall 

 first notice the experiments of Mr. Porrett, to whom we are 

 indebted for an opinion now very generally admitted to be true, 

 or at least probable, — that iron, carbon, azote and hydrogen 

 form a peculiar acid, which he has called ferrochyazic acid, and 

 which he considers as the acid of the salt in question. 



According to the latest experiments of Mr. Porrett* the 

 triple prussiate of potash is composed of 



1 atom ferrochyazic acid 53 



1 atom potash ... 48 



2 atoms water ... 18 

 1 atom ferrochya-1 T77 



zate of potash J * 

 Berzelius's analysis [Ann. de Chim. Sfc. t. xv. p. 144.) gives; 

 6 atoms carbon . . 36 ... 16-902 \ Cyanogen 

 3 azote .... 42 ... 19-718 J 36-620 



1 atom iron .... 28 ... 13-146 



2 atoms potassium 80 . . . 37*558 

 3 water . . ._27 . • . 12-676 



213 100- 



* Annals of Philosophy, vol. xiv. p. 298. 



\ It will be noticed that Mr. Porrett estimates the weight of an atom of 

 iron at only one half of what it is usually allowed to be. 



It 



